Morphological characteristics of platform margins along the Kaijiang-Liangping Trough and their influences on reservoir development in the Sichuan Basin
During the Late Permian Changxingian period,the depositional pattern of the Sichuan Basin was influenced by the spreading of Mianlüie Ocean and regional extensional stress,and the Kaijiang-Liangping Trough was developed in the north of the basin.The morphological characteristics of platform margins and the major controlling factors of reef-shoal complexes development on both sides of the Trough need to be defined.Based on the analysis of regional tectonic and depositional background,the reflectance signatures of reef-shoal complexes in 2D and 3D seismic and drilling data were integrated to describe the variations of platform margins morphology along the Trough during the Changxingian period.Seismic reflection patterns and geological models were built for reefshoal complexes on platform margins of different types,and the major controlling factors and distribution patterns of the reservoirs were analyzed.Three conclusions were obtained as follows:(1) The profile of platform margins on the east and west sides of Kai-jiang-Liangping Trough during the Changxingian period can be divided into two major categories,i.e.fault-controlled steep slope type and ramp type.Four sub-types of platform margins are defined,including fault-steep slope type,steep slope type,ramp-slope break type,and ramp type.(2) The morphological characteristics of platform margins on the east and west sides of Kaijiang-Liangping Trough are the key factors controlling the scale of reef-shoal complexes,depositional patterns,and reservoir properties.(3) Dolomitization,multi-stage dissolution,and fracturing are the key factors for improving reservoir qualities in reef-shoal complexes.Favorable reservoirs are mainly located on the top of reef-shoal complexes along the steep slope on platform margins,or along basement faults.
Sichuan BasinLate PermianKaijiang-Liangping Troughmorphology of platform marginreef-shoal complexreservoir characteristicsdiagenesisdepositional pattern